As
for the lever inside of the spool box that's on the right side, above the
slotted spindle, the lever in my Lauter was designed to lock the spindle
in place. As to why Lauter decided to incorporate such a function,
the only thing I can figure is that it prevents the unit from being used
if the person attempting to use it (a) wasn't aware of the levers existence
or (b) was too small/short to reach the lever.

Now I'm not saying Lauter purposely installed a device that made it
difficult for youngsters or inexperienced users from using the player,
but I've never been able to come up with any logical reason for a "spindle
lock".